From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756807AbZBEDl0 (ORCPT ); Wed, 4 Feb 2009 22:41:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752166AbZBEDlO (ORCPT ); Wed, 4 Feb 2009 22:41:14 -0500 Received: from smtp118.mail.mud.yahoo.com ([209.191.84.167]:43876 "HELO smtp118.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752096AbZBEDlN (ORCPT ); Wed, 4 Feb 2009 22:41:13 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=ENmudXF0ADRkrok1mqLU/az8YbaiwgrwMhpZJ6kOfsSRrQKTr4T1IL+45um/ayQG/KwkEQU+sj+NMTEmPl5dSJEPs7M3r1n3Oe7VSLQsfMxZNpbkdBs1xg4r8DToGGKMfm8YXvKMT9thr041aeY8B6ai4vdNBX5mP0G3vea47qw= ; X-YMail-OSG: VV0l6tEVM1njWs7h0I32cETseR77ZThzp06iRvoRG1p_mw65XjwmifMKmDS663eZDCvnbwq8JeQLDXA.KmMKLnCLvJ8yNIfCAS7dw7C1La1AyV1Yw3F20.PVe1ts0SdMyzPKrLf3NNwrBOBITojcCiGvpZDDMLska8Hua8_uJjCUVfrH6XM2N.4wwYrtXQ-- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Chris Mason Subject: Re: Commit 31a12666d8f0c22235297e1c1575f82061480029 slows down Berkeley DB Date: Thu, 5 Feb 2009 14:40:41 +1100 User-Agent: KMail/1.9.51 (KDE/4.0.4; ; ) Cc: "Zhang, Yanmin" , Jan Kara , Andrew Morton , linux-fsdevel@vger.kernel.org, LKML , npiggin@suse.de References: <20090130012315.GB19554@duck.suse.cz> <200902031311.02378.nickpiggin@yahoo.com.au> <1233677565.7246.15.camel@think.oraclecorp.com> In-Reply-To: <1233677565.7246.15.camel@think.oraclecorp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200902051440.42176.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 04 February 2009 03:12:45 Chris Mason wrote: > On Tue, 2009-02-03 at 13:11 +1100, Nick Piggin wrote: > > The interesting thing is why is this causing such a slowdown. If there is > > only a single main file active in the workload, then I don't see why this > > patch should make such a big difference. In either case, wouldn't pdflush > > come back and just start writing out from the start of the file anyway? > > Perhaps the difference is that without the patch, pdflush will return > after running congestion_wait()? This would give bdb and iozone a > chance to fill in more pages, and increases the chances we'll do > sequential IO. That's a possible explanation. I'll do some iozone runs and see if I can work out what's going on. If we can distill the "goodness" of the previous offset-wrap behaviour without reverting to make writeout more offset dependent, that would be nice -- it might even benefit other cases that weren't previously hitting the offset wrap case. Worst case, if we can't come up with something simple and obvious for 2.6.29, we can restore the old behaviour until we can come up with something better. Thanks, Nick